Since the parlay consists of more then 2 teams to win, your chances are decreased much more then if it was only 1 game you had to win
Quote from https://www.thelines.com/betting/parlay/
Parlay betting is also popular with sportsbook operators because they’re very difficult to win and that makes them profitable. According to UNLV Gaming, sportsbooks in Nevada have a win percentage on parlays of 31.17% since 1992. For reference, they didn’t win more than 7% from other bet types.
I would never risk big money on parlays. Risking small amounts like $1 or $2 makes sense here. Most people prefer 3 round parlays due to the risk vs reward ratio which is optimal in this case. Parlays are good examples of Low risk-Big reward betting type.